Scraper



March 5, 1963 F. G. REUTER ETAL 3,079,998

SCRAPER Filed June 9, 1958 FlG.-l FIG-2 3,079,998 SCRAPER Franz G. Renter, Lemforde, Hannover, and Ulrich Nehse,

' Roggenberg, Barnstorf, Hannover, Germany Filed Eune 9, 1958, Ser. No. 740,867 Claims priority, application Germany June 15, 1957 4 Claims. (Cl. 166-176) This invention relates to a scraper for removing parafiin deposits. More particularly, the invention is concerned with a scraper adapted to clean the inlet conduit (raisingtubes) of oil-Well pumps and similar oil carrying conduits.

It is Well known to use metallic scrapers for preventing the formation of paraffin deposits in the conduits through which oil is raised by oil-well lift pumps. The scrapers of conventional design, which are mounted on the sucker rods of the pumps, consist of a tubular metallic body having on its periphery radial projections which perform the scraping work.

Such conventional scrapers have serious disadvantages. Thus, they damage the internal coating of the tubes on account of their hardness. As a result, the tubes lose the protection afforded by the coating and progressively become exposed to corrosion. Another disadvantage attendant upon the conventional metallic scrapers is the fact that in case of breakage fragments of the scrapers are likely to get into the pump mechanisms, which may result in the destruction of the whole pump. Furthermore, the attachment of the conventional scrapers to the sucker rods presents serious difiiculties. The conventional scrapers are fastened to the rod by means of wedges or similar devices. However, it is almost impossible to firmly secure the scrapers to the rod in this manner without damaging the parts. Finally, the metallic scrapers heretofore used are converted into piston-shaped bodies within relatively short periods of operation due to parafiin depositing on the scrapers. This necessitates frequent shut-downs of the pumps in order to dismantle the sucker rods and to clean the scrapers.

It is therefore a primary object of the present invention to provide a paraifin scraper which causes no damage to the conduits or pump parts. Another object of the invention is to provide a parafiin scraper which can be easily and securely mounted on the sucker rods. A further object is to provide a parafiin scraper which can be used over long periods without the necessity to interrupt pumping operations for replacement or cleaning of broken or disabled parts. Still further objects will become apparent from the following description with reference to the accompanying drawing which illustrates a parafiin scraper made in accordance with and embodying this invention.

In the drawing:

FIGURE I is a view in elevation of a paratfin scraper constructed in accordance with one embodiment of the invention, said scraper comprising two halves.

FIGURE II is a view in longitudinal section, taken along the line 11-11 of FIGURE I, and showing the internal aspect of a scraper half.

In accordance with this invention, generally speaking, the foregoing objects and others are accomplished by providing a paraflin scraper comprising a body portion having two half sections made of a hard elastic material, said halves together forming a hollow cylinder adapted to enclose the sucker rod of a pump, said cylinder halves being held together and fastened to the sucker rod by means of coupling clamps.

The scrapers of the present invention may be made of any suitable material. Materials that combine elasticity with abrasion resistance are preferred materials of construction for the scrapers. A particularly suitable material is polyurethane rubber made from polymeric by- 3,h79,% Patented Mar. 5, 1963 2 droxyl compounds, such as hydroxy-l polyesters and hydroxyl polyethers, and organic diisocyanates, using processes that are known per so (see, for example, US. Patents 2,620,516; 2,621,166; 2,729,618; 2,764,565 and 2,778,- 810).

Representative of the starting materials which may be utilized in the preparation of polyurethane rubber is a mixture of parts by weight of a hydroxyl polyester prepared by esterifying about 11 moles of adipic acid with about 12 moles of ethylene glycol, and 30 parts by weight of 1,5-naphthylene diisocyanate. The isocyanatemodified polyester thus formed is cross-linked by addition of 7 parts of butylene glycol. It may be advantageous to include small amounts of molybdenum disulfide and silicon oil in the polyurethane rubber formulation to improve the abrasion resistance and other characteristics of the. finished product.

The use of polyurethane rubber for the scrapers of this invention ofiers the advantage that it constitutes a material of construction which can be tailor-made to meet the desired specifications, such as hardness and elasticity. Thus, the scrapers of the invention may be adapted to a great variety of applications. It is also possible to use two or three scrapers of different hardness in a given operation, depending upon existing conditions. However, for most applications, polyurethane rubber having a Shore hardness of about 9Q", an average elasticity of about 35% and an elongation at break of about 500% has been found to be suitable.

Although polyurethane rubber is the preferred material of construction for the scrapers of this invention, other materials combinin'g'elasticity with abrasion resistance may also be employed, as mentioned above.

An important feature of the scrapers of the invention is that they do not get stuck in the tubes due to paraffin deposits and clogging, since they are parafrin-repellent, if made of a suitable material such as polyurethane rubber.

According to a preferred embodiment of the present invention, each of the two scraper halves is provided with a scraping element which is a helical rib extended radially from the periphery of the scraper half. The ends of the ribs start and terminate in diametrically opposite, longitudinally displaced relation on said scraper half body portion whereby each rib describes half a screw turn. Each scraper rib begins on the lower portion of one side and ends on the upper portion of the opposite side at points approximating the dividing plane between the two scraper halves. In both halves the helical ribs have the same pitch and direction of curvature. It is advantageous to cast each scraper half with its helical scraper rib in one piece, using a liquid reactive mixture capable of forming cast polyurethane rubber upon cross-linking and solidification. Also, the helical ribs are disposed so as to terminate at each end in spaced relation to flange portions extending outwardly from the ends.

In order to have therequired resistance to deformation, the scraper ribs are given a wide cross-section at their base on the cylindrical portion of the scraper halves from which they project, the cross-section tapering oft toward the outer circumference. Preferably, these ribs have a trapeziform, cross-section, in which the narrow, outer side edge portion is inciined slightly toward the body portion to provide a substantially line-contact scraping edge.

The two coupling clamps provided for fastening the scraper halves to the connecting rod are tightened by means of screws so as to press the interior surface of the scraper securely against the connecting rod. Flange portions at the ends of the respective body portion sections match and prevent the coupling clamps from sliding off, the coupling clamps occupying the free area between the flanges and the scraper ribs.

Owing to their design and construction, the scrapers ac- 3 cording to the present invention avoid the disadvantages of the heretofore-used metallic scrapers. The polyurethane rubber preferably used as material of construction is abrasion resistant and yet elastic enough not to damage the skin of the tubes of the pump. As a result, the service life of the tubes is considerably lengthened. Furthermore, the elasticity of the material of construction prevents breakage of the new scrapers. However, if a scraper according to this invention should break contrary to expectations, chances are that the pump will remain unharmed, thanks to the flexibility of the fragments. Another great advantage of the new scrapers is the particular manner in which they are fastened to the connecting rods. The type 'of fastening permitted by the scrapers of the invention is not only simple but also extremely firm. It results in a secure attachment of the scrapers to the connecting rods, thus preventing an undesirable loosening as encountered with the conventional scrapers. Finally, if made of polyurethane rubber, the new scrapers are paraffin-repellent so that clogging due to paraflin deposits is avoided.

Referring more particularly to the drawing, the scraper represented in FIGURES I and II comprises the two elastic body portion halves 1 and 2 which carry on their periphery the helical scraping ribs 3 and 4, each scraping rib forming half a screw turn. The scraper halves are provided with the peripheral flanges 5 and 6 which prevent the coupling clamps 7 and 8 from sliding oil the scraper. Clamps 7 and 8 occupy an area provided between the flanges 5 and 6 and the scraping ribs 3 and 4. Screws 9 and 10 are provided to tighten the clamps thereby pressing the scraper halves 1 and 2 together and fastening them firmly to the sucker rod (not shown in the drawing).

While certain representative embodiments and details have been shown for the purpose of illustrating this invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing fiom the spirit and the scope of the invention.

What is claimed is:

1. A resilient scraping device for removing parafiin deposits from the inside wall of an oil-carrying conduit, said device comprising a tubular body formed of two opposed semi-cylindrically shaped sections of paraflin-repellent abrasion-resistant resilient polyurethane rubber adapted to be positioned in said conduit circumferentially 'disposed about a connecting rod disposed in said conduit for reciprocal movement therein, each of said sections of said body including a scraping element in the form of a helical rib, and flanges at the upper and lower ends of said entire periphery of said inside wall of said conduit.

3. A resilient scraping device for removing 'paraffin deposits from the inside wall of an oil carrying conduit,

comprising a tubular body formed of two opposed abutting semi-cylindrically shaped sections of abrasion-resistant resilient parafiin-repellent polyurethane rubber adapted to be positioned in said conduit circumferentially disposed about a connecting rod disposed for reciprocal movement in said conduit, coupling means for holding said two sections together in fixed position around said rod for conjoint movement with said rod, each of said sections including a single scraping element in the form of a helical rib describing substantially half a screw turn beginning on the lower portion of one side of a section and ending on the upper portion of the opposite side of said section, both helical ribs running in the same direction whereby said ribs allow the free passage of oil through said conduit while contacting substantially the entire periphery of said inside wall of said conduit.

4. A scraping device according to claim 3, wherein said tubular body is formed with an annular flange, and said coupling means includes a clamp disposed between said flange and said ribs.

References Cited in the file of this patent UNITED STATES PATENTS 116,118 Voelker June 20, 1871 1,460,632 Wigle et a1. July. 3, 1923 1,600,578 Crickmer Sept. 21, 1926 1,634,094 Cook et al June 28, 1927 1,897,507 Morgan t. Feb. 14, 1933 2,712,853 Irwin July 12, 1955 2,781,100 Pyle et a1 Feb. 12, 1957 2,793,917 Ward May 28, 1957 2,813,697 Swart Nov. 19, 195.7 2,838,121

Coyle June 10, 1958 

1. A RESILENT SCRAPING DEVICE FOR REMOVING PARAFFIN DEPOSITS FROM THE INSIDE WALL OF AN OIL-CARRYING CONDUIT, SAID DEVICE COMPRISING A TUBULAR BODY FORMED OF TWO OPPOSED SEMI-CYLINDRICALLY SHAPED SECTIONS OF PARAFFIN-REPELLENT ABRASION-RESISTANT RESILIENT POLYURETHANE RUBBER ADAPTED TO BE POSITIONED IN SAID CONDUIT CIRCUMFERENTIALLY DISPOSED ABOUT A CONNECTING ROD DISPOSED IN SAID CONDUIT FOR RECIPROCAL MOVEMENT THEREIN, EACH OF SAID SECTIONS OF 